Windows not found by os-prober
I recently bought a new computer (a Lenovo IdeaCentre G5 in case someone is
curious). When installing archlinux (in dual boot), I couldn’t get
os-prober to detect Windows even though I could see all the Windows file in
/boot/EFI/....
I eventually just manually added a grub entry
menuentry 'Window' {
	search.fs_uuid <UUID>
	chainloader /EFI/Microsoft/Boot/bootmgfw.efi
}
Where you can get the UUID of your /boot partition with blkid. Interesting
enough if you put the wrong uuid, grub will complain but will still boot Windows.